//part1:C02:ex2.41.cpp
#include <functional>
#include <iostream>
#include <istream>
#include <ostream>
#include <string>

using namespace std;
class Sales_data
{
    friend std::istream& operator >> (std::istream&, Sales_data&);
    friend std::ostream& operator << (std::ostream&, const Sales_data&);
    friend bool operator < (const Sales_data&, const Sales_data&);
    friend bool operator == (const Sales_data&, const Sales_data&);
public:
    Sales_data() = default;
    Sales_data(const std::string &book): bookNo(book) {}
    Sales_data(std::istream &is) { is >> *this; }
public:
    Sales_data& operator += (const Sales_data&);
    std::string isbn() const { return bookNo; }    
private:
    std::string bookNo;
    unsigned units_sold = 0;
    double sellingprice = 0.0;
    double saleprice = 0.0;
    double discount = 0.0;        
};

inline bool compareIsbn(const Sales_data &lhs, const Sales_data &rhs)
{ return lhs.isbn() == rhs.isbn(); }

Sales_data operator + (const Sales_data&, const Sales_data&);
inline bool operator == (const Sales_data &lhs, const Sales_data &rhs)
{
    return lhs.units_sold == rhs.units_sold &&
        lhs.sellingprice == rhs.sellingprice &&
        lhs.saleprice == rhs.saleprice &&
        lhs.isbn() == rhs.isbn();
}

inline bool operator != (const Sales_data& lhs, const Sales_data &rhs)
{
    return !(lhs == rhs);
}

Sales_data& Sales_data::operator += (const Sales_data & rhs)
{
    units_sold += rhs.units_sold;
    saleprice = (rhs.saleprice * rhs.units_sold + saleprice * units_sold)/
                    (rhs.units_sold + units_sold);
    if (sellingprice != 0)
        discount = saleprice / sellingprice;                    
    return *this;        
}

Sales_data operator + (const Sales_data& lhs, const Sales_data& rhs)
{
    Sales_data ret(lhs);
    ret += rhs;
    return ret;
}

std::istream& operator >> (std::istream& in, Sales_data& s)
{
    in >> s.bookNo >> s.units_sold >> s.sellingprice >> s.saleprice;
    if (in && s.sellingprice != 0)
    {
        s.discount = s.saleprice / s.sellingprice;
    }
    else
    {
        s = Sales_data();
    }
    return in;
}

std::ostream& operator << (std::ostream& out, const Sales_data& s)
{
    out << s.isbn() << " " << s.units_sold << " "
        << s.sellingprice << " " << s.saleprice << " " << s.discount;
    return out;        
}

int main(void)
{
    Sales_data book;
    std::cout << "Enter sales records:\n";
    while (std::cin >> book) 
    {
        std::cout << "ISBN, volume, source price, real price, dicount: ";
        << book << std::endl;
    }
    Sales_data trans1, trans2;
    std::cout << "Enter two same ISBN records: " << std::endl;
    std::cin >> trans1 >> trans2;
    if (compareIsbn(trans1, trans2))
    {
        std::cout << "total info: ISBN, volume, source price, real price, discount :"
        << trans1 + trans2 << std::endl;
    }
    else
    {
        std::cout << "two differences of ISBN of two records:" << endl;
    }

    Sales_data total, trans;
    std::cout << "Enter some same ISBN of sales records.";
    if (std::cin >> total)
    {
        while (std::cin >> trans)
        {
            if (compareIsbn(total, trans))
            {
                total = total + trans;
            }
            else
            {
                std::cout << "differences of the ISBN" << std::endl;
                break;
            }
        }
        std::cout << "new total info: ISBN, volume, source price, real price, discount :"
            << total << std::endl;
    }
    else
    {
        std::cout << "No datas!" << std::endl;
        return -1;
    }

    int num = 1;
    std::cout << "Enter some records: " << std::endl;
    if (std::cin >> trans1) 
    {
        while (std::cin >> trans2)
        {
            if (compareIsbn(trans1, trans2))
            {
                num++;
            }
            else
            {   // ISBN differences
                std::cout << trans1.isbn() << "total of "
                    << num << " sales records." << std::endl;
                trans1 = trans2;
                num = 1;    
            }
        }
        std::cout << trans1.isbn() << "total of "
            << num << "sales records." << std::endl;
    }
    else
    {
        std::cout << "No datas!" << std::endl;
    }

    return 0;   
}
